This research project will define the intracortical patterns of neural activity that underlie visual evoked potentials and the endogenous event related potentials (ERP) associated with discriminative performance. Old world monkeys will be employed as an animal model of human ERP generation. Methods for concurrent recording of field potentials and multiple unit activity (MUA), augmented by current source density (CSD) analysis will be used to examine the effect of manipulating stimulus and task variables on intracortical activity. These studies are intended to bridge the gap between investigations of scalp recorded ERP in humans and the more detailed analyses of intracortical activity that can only be carried out in experimental animals.